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PM49260: PM12195 CAUSES A DEADLOCK ON /ETC/MTAB IF THE VOB IS NFS STORED AND THE UNDERLYING NFS STORAGE IS NOT YET MOUNTED

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APAR status

  • Closed as program error.

Error description

  • PM12195 causes a deadlock on /etc/mtab if the VOB is NFS stored
    and the underlying NFS storage is not yet mounted
    
    
    
    ClearCase 7.1.2.4
    
    
    
    RedHat 4 Update 8 (deadlock)
    RedHat 5 or SuSE 10 SP3 (10 second delay for each VOB)
    
    
    Description of Problem:
    
      1)  A 'cleartool mount' command will generate an RPC call to
    the mntrpc_server, and the mntrpc_server forks mount.mvfs
      2)  mount.mvfs obtains a file lock on /etc/mtab to prevent
    corruption of the mtab file
      3)  mount.mvfs then proceeds to try and mount the VOB.  It
    traverses the VOB storage path which, if not already mounted,
    triggers an automount of the NFS storage
      4)  Automount eventually calls /bin/mount to do the mount.
    Mount then attempts to take a lock on /etc/mtab and finds it
    locked and so waits
      5)  mount.mvfs is waiting on mount to finish mounting the NFS
    storage and now the Automount mount is waiting on a lock held by
    mount.mvfs to be freed to allow the VOB storage to me mounted
    
    On RedHat 5.3 and SuSE 10.3 the attempt to take the lock by
    mount times out after 10 seconds and fails, leading to a 10
    second delay per VOB to be mounted at boot. On RedHat 4.8, the
    timeout never occurs and the system hangs indefinitely.
    
    
    Workaround:  none
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    The problem was a locking conflict between the MVFS mount
    and the automounter, in the particular case where the VOB
    storage had become unmounted after a time interval, and
    needed to be re-mounted by the automounter.
    

Problem conclusion

  • This problem is fixed in ClearCase 7.1.1.8, 7.1.2.5, and
    8.0.0.1.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM49260

  • Reported component name

    CLEARCASE UNIX

  • Reported component ID

    5724G2901

  • Reported release

    712

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2011-10-04

  • Closed date

    2011-12-16

  • Last modified date

    2011-12-16

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

Fix information

  • Fixed component name

    CLEARCASE UNIX

  • Fixed component ID

    5724G2901

Applicable component levels

  • R712 PSN

       UP

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Document Information

Modified date:
16 December 2011